Advanced Processing Methods for CeFe₁₂-Based Permanent Magnets Phases with Narrow Stability Regimes

Projections expect the demand for permanent magnets to double by 2030 when it will exceed the supply of neodymium-based magnets by far. The fastest market growth is foreseen in wind energy and electric vehicles. Economies preparing for a green energy transition are therefore looking for alternative technologies such as permanent magnets based on the cheap and abundant rare earth metal cerium. Promising performance has been demonstrated in thin films and powders of the intermetallic phase CeFe_12-xTi_xN with ThMn₁₂ structure, but manufacturing of bulk magnets, essential for commercialization, remains a major obstacle. Besides the realization of fully dense material and microstructure optimization, the thermodynamic instability of these materials results in a narrow window of processing conditions and has hitherto prevented the realization of optimum performance. Hitherto, the majority of works have focused on the influence of substituting Fe for Co, Mo, Ga, Ti or V on the phase stability and magnetic properties in cast material or thin films.<br/>We have investigated the suitability of advanced powder processing methods such as laser powder bed fusion and spark plasma sintering for the preparation of bulk magnets from powders of the CeFe_12-xTi_xN phase. The rapid solidification rates of the former and the mild sintering conditions of the latter method are ideally suited for the consolidation of powder materials that defy conventional processing methods. After establishing process-structure-property relationships for the material, we have investigated the processing regimes for obtaining suitable microstructures for permanent magnet performance while retaining the targeted chemical composition of the intermetallic phase. Work performed at LLNL under contract DE-AC52-07NA27344.